Influence of the GDL and assembly mode of a PEM cell on the ethanol revalorization into chemicals

Abstract

This work reports the influence of the gas diffusion layer (GDL) and cell assembly mode on the ethanol revalorization through the electro-reforming process, focusing on hydrogen and value-added organics (acetaldehyde, ethyl acetate and acetic acid) products distribution. All essays were conducted in a Proton Exchange Membrane (PEM) Electrolysis Cell of 5 cm2 at mild conditions (80 °C and 1 atm) on commercial Pt/C (cathode) and PtRu/C (anode) catalysts. In this scenario the selection of a proper GDL and way of assembly proves to be a critical step influencing the electrochemical performance. Carbon paper-based configurations exhibited the best profiles in terms of electro-catalytic activity, reaching high current density values (600–720 mA·cm−2 at 1.4 V of cell potential), which are close to those obtained in alkaline media. Conversely, that based on porous titanium showed a lower efficiency (less than a half) due to the mass transfer limitations of reactants and products through the GDL, as confirmed by the electrochemical impedance spectroscopy essays. Regarding organic product distribution, non-assembled carbon paper-based configuration displayed the best results, increasing the production of value-added organics and shifting the acetic acid generation to lower cell potential values (close to 0.7 V). This was attributed to the direct deposition of the catalytic layers over the membrane instead of over the carbon GDL, which enhances the reactants and ions transport, improving the electrochemical activity. In addition, this configuration showed quite lower energy requirements for H2 production (<20 kWh·kgH2−1 at 0.8 V) in comparison with a PEM water electrolyzer stack.